1. Plant Cell Structure Unit
Botany
Plant Cell Structure Unit
Textbook Reading Requirement
Chapter 3 (pp )
Objectives: To describe the basic structure of typical plant cells.
To describe, in detail, cellular structures unique to
plant cells.*
To observe and draw examples of plant cells using
the microscope.

2. ( )
Robert Hooke, Marcello Malpighi, Nehemiah Grew,
Anton von Leeuwenhoek, Jean Babptist de LaMarck
Renee J.H. Durochet, Robert Brown, Matthias Schleiden,
Theodor Schwann, Rudolph Virchow, Louis Pasteur,
Edward Buchner.
Cell Theory
-All living things and only living things are composed of cells
-Cells are the structural unit of living things.
-Cells arise from other living cells.

3. Prokaryotic Cells- cells lacking membrane bounded organelles
(w/o nucleus)
Blue green algae: Anabaena

4. Eukaryotic Cells- cells with membrane bounded organelles w/ nucleus
Algae: Chlamymadomonas

5. PROKARYOTIC CELLS EUKARYOTIC CELLS
1. Lacks a nuclear membrane
2.Has a single long strand of DNA
and several plasmids.
3. Have no membrane bounded
organelles
4. Asexual reproduction by binary
fission
5. Sexual reproduction unknown.
EUKARYOTIC CELLS
1. Have a nuclear membrane
2. Have two to hundreds of
chromosomes per cell.
3. Have membrane bounded
organelles
4. Asexual reproduction by mitosis
5. Sexual reproduction involves the
fusion of sex cells.

6. Cells Size of cells vary: smallest (bacteria) 0.5 micrometers
most (higher plants) micrometers
largest (unique!) cm - 20 cm
Due to the typical small size of cells, the number of cells in an
average higher plant is “astronomical”!
1 mature leaf of a pear tree = 50 million cells (est.)
1 mature pear tree = 15 trillion cells (est.)

7. “Trees have no bones or similar internal support structures as do animals.
yet, they are able to support branches & leaves weighing many tons.”
“A single mature redwood exceed the mass and volume of the largest
land animals by more than a hundred times.”
“The wood from a single redwood could support the combined weight
of a thousand elephants.”
How?
The combined strength of its cell walls!

8. Robert Hooke’s sketches
Cell Wall Basics
Cell Wall- nonliving boundary, produced by the living components
of the cell that supports and protects.
- strong, rigid (with a degree of elasticity)
- typically composed of cellulose
Robert Hooke’s sketches
of cork cells
S.E.M. micrograph of cork cells
S.E.M.

9. Hemicellulose. S.E.M. 25,000X Electron micrograph of
a plant cell wall showing
cellulose microfibrils.
Microfibrils are held
together by a glue-like
substance termed
Hemicellulose.

10. Additional Components of the Cell Wall
Most plant cells possess thin, elastic cell walls- Primary Cell Wall
Cell walls are separated from one another by the middle lamella.
Middle lamella is composed of pectin (thick, gelatinous polysaccharide)
(Cellulose & Hemicellulose)
(Pectin)

11. “The thickness of a plant cell wall can occupy from
Layers can be added to the primary cell wall providing
additional support - Secondary Cell Wall
Secondary cell walls are composed of additional layers of cellulose
Which may be impregnated with other substances:
Lignin - hardening agent (wood, shells of nuts)
Suberin and Cutin - waterproofing agents (bark, cork, leaves)
“The thickness of a plant
cell wall can occupy from
5% to 95% of a cell’s
total volume!”

12. Cell
Walls

13. S.e.m.
of wood

14. LIGNIN

15. SUBERIN

16. Movement of materials through cell walls involves Plasmodesmata.
Plasmodesmata are small strands of cytoplasm that connects one
plant cell to adjacent plant cells

17. Plastids
Plastids- group of plant cell organelles with a variety of functions.
Three Types of plastids: (based on color & function)
1) Chloroplast- green plastids / site of photosynthesis.
Contains chlorophyll and other pigments
T.E.M.

18. Stroma
Granum (Grana)
T.E.M.
10,000X
Thylakoids

19. 2. Leucoplast- plastids that are involved with food storage
Colorless; Primarily store starches and oils.
(amyloplasts, elaioplasts)
Development of a leucoplast

20. 3. Chromoplasts- type of plastid whose function is the storage
of certain pigments. (red, yellow, orange, blue).
These plastids give rise to the colors seen in
flower petals, fruits and other parts of certain
plants. (colorbodies)

21. Plastids are capable of changing from one type to another.
green tomato (chloroplasts) > red tomato (chromoplasts)
Potato (leucoplasts) > potato (chloroplasts)

22. Vacuoles
Organelles that act as storage sites for a variety of plant substances
(starch, sugars, oil, pigments, water, wastes) as well as maintaining
cell pressure (turgor).
Young plant cells have small vacuoles that are few in number. As cells mature their vacuoles increase in size and coalesce to form a single, large structure which may occupy 95% of the cell lumen.
The name given to the
Liquid found in plant cell
Vacuoles is cell sap.

23. Elodea

24. Starch grains in root tip cells.